Prior art safety devices have included pins or the like that are inserted through prong openings of an electrical plug such that adults can prevent children from receiving an electrical shock upon playing with the plug or from operating an electrical tool or appliance, etc. connected to the plug. Such prior art devices have required either a special tool or lock to secure the device to the plug.
U.S. Pat. Nos. 3,416,123 and 3,422,389 each disclose a plug block that defines holes for receiving the plug prongs. A cross bore of the block receives a pin that is inserted through the prong openings to secure the plug to the block. A lock associated with the block selectively secures the pin so as to retain the block on the plug in order to control use of the plug.
U.S. Pat. Nos. 3,345,600; 3,539,968; and 3,662,342 disclose electrical plug safety devices including brackets or housings that are stamped from sheet metal and secured through prong openings of an associated electrical plug in cooperation with the shackle of a lock. None of these devices has a construction that is both economical to manufacture as well as easy to use. For example, the 3,345,600 patent discloses an electrical plug locking device that is manufactured with a pivotal pin located between spaced legs of a stamped sheet metal housing. During use, the pin must be pivoted to an outwardly projecting position and then inserted through the prong openings of an associated plug whereupon the plug prongs are inserted into the housing so as to pivot the pin such that it can be secured by a lock. Such a device thus requires a relatively involved manual manipulation to retain the device to the plug. Likewise, the 3,539,968 patent discloses a two-piece device including a strap and an associated pin that are locked together with the pin extending through both the strap and the associated plug prong openings to secure the device to the plug, the problem with such a device being that the pin and the strap can become separated when not being used and either is thus easily lost. The safety device disclosed by the 3,662,320 patent includes a stamped metal slide assembly having two pieces whose construction is not particularly easy to manufacture so as to be capable of assembly in a sliding manner that locks the device through the prong openings of an associated electrical plug in cooperation with a lock.
U.S. Pat. No. 3,781,913 discloses a device that requires a screwdriver to secure a screw through a plug prong opening to a safety block in order to prevent use of the plug.
Also, small locks have previously been secured with the shackle thereof extending through one prong opening of an electrical plug.